Explanation:

In the given options, the correct answer is option 'B' Nagaland. Nagaland does not have a Scheduled Caste population. Let's understand the reason behind this.

Scheduled Castes:
Scheduled Castes (SC) are specified under the Indian Constitution as historically disadvantaged and discriminated groups. They are given special provisions for their social, educational, and economic upliftment. These provisions include reservations in educational institutions, government jobs, and other benefits.

Scheduled Castes in North-East States:
The North-Eastern states of India have a unique demographic composition compared to the rest of the country. These states have a significant tribal population, and the Scheduled Tribe (ST) communities are relatively more dominant. However, the Scheduled Caste population in these states is relatively smaller.

Mizoram:
- Mizoram has a Scheduled Caste population. Therefore, option 'A' is incorrect.

Nagaland:
- Nagaland does not have a Scheduled Caste population. The state is predominantly inhabited by various tribal communities, making up the majority of the population. Therefore, option 'B' is correct.

Manipur:
- Manipur has a Scheduled Caste population. Therefore, option 'C' is incorrect.

Assam:
- Assam has a significant Scheduled Caste population. Therefore, option 'D' is incorrect.

In Conclusion:
Among the given options, Nagaland is the only state where there is no Scheduled Caste population. The other options, Mizoram, Manipur, and Assam, do have Scheduled Caste populations, although their proportions may vary.